In 200 years, the human body temperature dropped from 37℃ to 36.5℃? Maybe it is the result of human health improvement

As we all know, we humans are mammals, and mammals are warm-blooded animals, which means that our body temperature is relatively constant. Why is this so? In fact, it is to facilitate the work of protein.

I am studying protein. Protein is actually the most important molecule in our cells. In particular, many proteins act as enzymes in our cells. Enzymes are what help some biochemical reactions to occur. Without the help and catalysis of enzymes, these biochemical reactions in nature may take a long time, such as hundreds of years, thousands of years, or even millions of years to complete. However, with the help of these enzymes, these biochemical reactions can be completed in an instant. Therefore, if we leave these enzymes composed of proteins, our lives will definitely stop.

However, these enzymes have a characteristic when they are working. We will measure their states at different temperatures and find that their curves are always like peaks - at relatively high temperatures, their working efficiency may be relatively low. As the temperature decreases, a peak appears, which means their working efficiency goes up. But when you lower it to a certain level, their working efficiency drops again. That is to say, to reach its maximum working efficiency, it must be at a most suitable temperature. In fact, for us humans, the most suitable temperature is our normal and healthy body temperature, which is 37 degrees Celsius.

So are all animals at this temperature? Definitely not. For example, the temperature of many birds is higher than 37 degrees Celsius. If you have ever held a hen, you may feel that the heat is constantly coming from the chicken's body. This is because the average body temperature of chickens is higher than that of humans. These relatively high body temperatures are actually beneficial for birds to fly. There are also many animals that are not warm-blooded animals at all. We also call them so-called cold-blooded animals or cold-blooded animals. For example, reptiles, such as crocodiles, always bask in the sun on the shore. In fact, it is to raise their body temperature by basking in the sun so that the enzymes in their cells can work better. If the temperature of the entire environment is very low, they can only hibernate. For example, the hibernation of snakes is actually mainly caused by too low temperatures.

Back to us humans, our normal body temperature is 37 degrees Celsius, but a word appeared: Celsius. We usually say body temperature and air temperature, we always say how many degrees Celsius, we are used to it, in fact, there is another relative one called Fahrenheit. I think many people may know that there are very few countries that still use the Fahrenheit temperature scale. There are really only a handful of them. One of the big countries is the United States. Then, it is actually very inconvenient to convert Fahrenheit and Celsius, because zero degrees Fahrenheit is not equal to 0 degrees Celsius. We know that zero degrees Celsius is the temperature at which pure water freezes under normal atmospheric pressure.

The picture comes from Tuchong.com

Zero degrees Fahrenheit is actually the temperature at which salt water freezes, which is about tens of degrees below zero, while 100 degrees Fahrenheit is the so-called normal human body temperature. At that time, the scientist used his wife's body temperature as a temperature scale of 100 degrees. Obviously, we know that this is unscientific, because human body temperature will change throughout the day, not to mention that there are great differences between people. For example, my normal body temperature will never reach 37 degrees Celsius, always hovering between 36.5 and 36.8 degrees Celsius. There are differences between people, and each person is different every day. At what time point and which person's temperature is 100 degrees? This is very unscientific. Now the Fahrenheit temperature scale is no longer defined by human body temperature. In fact, it is also like our Celsius temperature scale, which is defined according to different physical conditions, and then defines different freezing points and boiling points to define such a temperature.

The story of Fahrenheit temperature actually tells us that human body temperature is not a fixed value. It may be different for each person. Is this changing? Indeed, scientists have been monitoring the average body temperature of the entire human race for the past 200 years. With the support of a large amount of data, they found that our average body temperature has been declining. What is the rate? It is decreasing by 0.03 degrees Celsius every 10 years, that is, 0.3 degrees Celsius every 100 years. From 1800 to now, it has dropped by 0.6 degrees Celsius in more than 200 years. That is to say, our average body temperature has dropped from 37 degrees Celsius in 1800 to about 36.5 degrees Celsius.

Why is there such a significant decline? In fact, the exact reason behind it is still unclear. There are several hypotheses. I personally think that one of the more reliable hypotheses is related to the infection of pathogens. We all know that once our body is invaded by external pathogens and infected, we may have a fever. In fact, sometimes we don’t have such a severe fever, but just a slight increase in body temperature. This slight increase is beneficial for our immune system to eliminate these invading pathogens. In fact, in 1800, modern medicine had not yet been established. People at that time often had to coexist with these pathogens, that is, there might not be so-called healthy people. Then everyone’s body may have more or less pathogens. It is very likely that it is because of the existence of these pathogens that people’s body temperatures have been raised. Today, we all live relatively healthier lives, and it is rare for us to be invaded by other pathogens. So this may be one of the reasons why our average body temperature has been declining in the past 200 years. Of course, these hypotheses still need to be verified by more scientific data and scientific experiments before we can finally draw a definite conclusion.

This article is a work supported by Science Popularization China Starry Sky Project

Author: Ye Sheng

Reviewer: Tao Ning (Associate Researcher, Institute of Biophysics, Chinese Academy of Sciences)

Produced by: China Association for Science and Technology Department of Science Popularization

Producer: China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.